The cash Isa allowance will remain at £20,000, This is Money understands, after Rachel Reeves put the brakes on plans to cut it.
The Chancellor was widely expected to announce plans to slash the £20,000 tax-free allowance in the Mansion House speech.
Savers will still be able to put up to £20,000 a year into cash Isas with all the interest earned on savings being free from tax.
It was thought the allowance could be cut to £4,000 or £5,000 in a bid to get cash savers investing in the stock market and boost the economy.
However the Chancellor is understood to be seeking to consult more widely with banks and building societies about the best way to shift more money into investments.

The Government is keeping all aspects of savings policy under review as the Chancellor scrambles to fill a black hole in the country's balance books, it is understood.
The news will offer solace for savers who will not see any changes to the cash Isa for now, though wider Isa reforms have not been ruled out.
The u-turn comes after fierce backlash to the alleged changes to the cash Isa allowance from savers and industry figures alike.
Earlier this week The Building Societies Association penned a letter to the Government warning restrictions imposed on cash Isas could have unintended consequences on the housing market.
Namely, reducing funding for lending, driving up mortgage prices and triggering a housing market downturn.
'This,' it says, 'would undermine efforts to stimulate economic growth, including the Government's commitment to delivering 1.5million new homes'.
Adam French, consumer expert at rates scrutineer Moneyfacts Compare said the move would have sparked 'chaos in the housing market' due to mortgage costs rising.
A Treasury spokesperson said: 'Our ambition is to ensure people’s hard-earned savings are delivering the best returns and driving more investment into the UK economy.'
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